The demand for wireless communications is growing at a rapid pace, in particular, cellular phones, cordless phones, and wireless local area networks (LAN's). In general, all of the components within a hand held communication device should be of light weight, compact, low cost, efficient, and require a minimum amount of power consumption. A further trend is increasing frequency of operation, as for example, from 800 MHz to 2-10 GHz.
FIG. 1 Shows a simplified schematic diagram of typical prior art RF front end unit 10 of a typical duplex communication transceiver. RF front end unit 10 comprises antenna 12 coupled by lead 11 to antenna switch 14. Antenna switch 14 has a receiver path coupled by lead 15 through filter 16 and lead 17 to the receiver circuits of the transceiver. Another path couples the transmitter circuits of the transceiver via line 19 through filter 18, via line 21 through amplifier 20, via line 23 through filter 22 and via line 25 to antenna switch 14. Antenna switch 14 provides duplex communication by switching on demand between receiver chain 15-17 and transmitter chain 19-25. In modern communication systems, antenna switch 14 is, generally, an active device, typically a semiconductor device. As a consequence, it consumes power when it is in operation. Filters 16, 18 are typically SAW filters and filter 22 is typically a ceramic filter. Antenna 12 is typically a small whip or blade antenna.
A limitation of the prior art is that antenna 12, antenna switch 14, filter 16 and filter 22 employ different technologies in the form of separate components which must be interconnected using, for example, a circuit board and external wiring. Each of components 12, 14, 16, 22 is typically individually packaged. Thus, RF front end elements 24 consume more power and occupy more space than is desired for advanced duplex communication systems.
Accordingly, there is an ongoing need to reduce the size and power consumption, and simplify the construction of the RF front end elements needed to provide duplex communication and antenna functions within modern telecommunication transceivers and thereby obtain an improved radio. It is an advantage of the present invention, that the antenna switch of the radio is eliminated and the antenna and signal separator are combined in a single integrated element of comparatively small size.